The FBI thinks it's found the person who leaked top secret intelligence about Russia

Acting FBI Director Andrew McCabe waits before the Senate Intelligence Committee in the Hart Senate Office Building on Capitol Hill May 11, 2017 in Washington, DC.
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The FBI arrested a federal contractor from Augusta, Georgia, on Saturday and charged her with leaking top-secret intelligence to a news outlet, the Justice Department said Monday.

NBC News confirmed that 25-year-old Reality Leigh Winner was arrested on charges involving the leak of a top-secret National Security Agency document to The Intercept that detailed a Russian hacking operation targeting US voting systems.

Winner was hired by Pluribus International Corporation in early February and held top secret security clearance, the Justice Department said. The company's clients include the Defense Intelligence Agency, US Army, and US Central Command.

The FBI special agent who wrote the affidavit in support of Winner's arrest alleges that she printed out the document from her work computer on May 9, 2017, and mailed it to a "News Outlet." The outlet then showed the document to the NSA —referred to as "the Government Agency" — in order to confirm its authenticity.

"The U.S. Government Agency examined the document shared by the News Outlet and determined the pages of the intelligence reporting appeared to be folded and/or creased, suggesting they had been printed and hand-carried out of a secured space," the agent, Justin Garrick, wrote.

"The Government Agency conducted an internal audit to determine who accessed the intelligence reporting since its publication," he wrote. "The U.S. Government Agency determined that six individuals printed this reporting. WINNER was one of these six individuals. A further audit of the six individuals' desk computers revealed that WINNER had e-mail contact with the News Outlet. The audit did not reveal that any of the other individuals had e-mail contact with the News Outlet."

Winner "admitted intentionally identifying and printing the classified intelligence reporting at issue" and mailing it to the outlet, according to the affidavit.

In a statement, Vivian Siu, the director of communications at The Intercept, said the document was provided to the outlet anonymously.

"The Intercept has no knowledge or identity of the source," Siu said.

One additional clue that points toward the NSA document as what Winner leaked is that it has a declassification date of 05/05/2042. The affidavit says that the leaked top-secret document was first published "on or about May 5, 2017."

"Exceptional law enforcement efforts allowed us quickly to identify and arrest the defendant," Deputy Attorney General Rod Rosenstein said in a statement. "Releasing classified material without authorization threatens our nation's security and undermines public faith in government. People who are trusted with classified information and pledge to protect it must be held accountable when they violate that obligation."